Comparison of slit lamp based anterior chamber depth measurement with Lenstar LS 900 and its correaltion with Anterior Chamber Angle Assessed by Anterior segment OCT

Background The anterior chamber depth (ACD) is a vital metric for evaluating angle-closure glaucoma and for strategizing cataract surgery or phakic intraocular lens (IOL) implantation. This study aimed to evaluate the mean difference in anterior chamber depth (ACD) measurements obtained by means of Smith’s technique and the Lenstar 900, as well as to ascertain its association with the anterior chamber angle (ACA) using anterior segment optical coherence tomography (AS-OCT). Methods This cross-sectional analytic study comprised 70 clean-corneaed people over 40 of both genders. All patients had a basic slit lamp examination of the anterior segment, including Smith's 1979 technique of measuring axial anterior chamber depth (ACD). Then, a variety of refractive states corresponding to axial length were determined by combining non-contact optical biometry (Lenstar 900) with anterior segment optical coherence tomography (AS-OCT). Results A significant difference was observed between Smith ACD (3.08 ± 0.52) and Lenstar ACD (3.22 ± 0.49) (P < 0.001), with a mean difference of -0.13 (-0.19: -0.07 CI), particularly evident in patients with short and average axial lengths; Smith’s technique tends to underestimate the ACD relative to Lenstar 900. This variation is insufficient to be clinically or practically important when contemplating cataract surgery or intraocular lens implantation. The estimations of ACD derived from Smith's technique show a favorable association with ACA measurements obtained using AS-OCT. Conclusions The Smith method enables accelerated measurement of axial ACD without the need for specialized slit-lamp attachments. It is a realizable, non-invasive, and rapid technique that is appropriate for the initial assessment of patients with shallow anterior chambers.